1. Field of the Invention
The present invention is related to a method and related apparatus capable of improving image quality of a liquid crystal display device, and more particularly, to a method and related apparatus which can reduce flickering phenomena and increase the grey levels of the liquid crystal display device.
2. Description of the Prior Art
As technology advances, not only the functions of various IT products become even more complicated, but their designs are also becoming slimmer and of less weight. At the same time, many popular products, like the wireless phone, the personal data assistant (PDA) and the video game controller are using a liquid crystal display (LCD) device as the apparatus to present visual information. Compared with other kinds of display device, the LCD device has several advantages like light weight, thin thickness and reasonable price. At present, for the handheld or portable IT product, few other display technologies may challenge the dominant role of the LCD devices.
Please refer to FIG. 1, which illustrates a schematic diagram of display elements located in a liquid crystal display device 10 according to the prior art. Generally, the liquid crystal display device 10 comprises a large number of display elements or pixels lined up as multiple columns and rows. Furthermore, a color display element is to overlay a display element with a color filter selected from the well-known three primary colors, which are red, green and blue, respectively; then, various kinds of colors can be realized by combining the lights outputted from the neighboring display elements of three primary colors. When the grey levels increase for each of the display elements, the total number of colors which can be displayed will be increased to the third power. For example, if the total grey levels of each display elements are equal to and can be represented by an 8-bit digital number, which corresponds to 256 grey levels, then the total number of colors which can be displayed by the three display elements of three primary colors would theoretically amount to 256*256*256 (=16,777,216).
For every display element, there exists a proprietary electrode, which is used for applying a voltage signal to control the optical characteristics of the liquid crystal of the display element; that is to say, by controlling the voltage of the electrode, the liquid crystal of the display element can modulate the polarization angle of the incoming light, such that the display element can behave as an optical switch. By taking the normally black liquid crystal display device as an example, when the voltage difference between the proprietary electrode and the common electrode increases, the light transmittance of the display element will be increased according to the voltage difference. Therefore, when a pixel data is input to the liquid crystal display device 10, the liquid crystal display device 10 can adjust the voltage of the proprietary electrode of each display element according to the value of the pixel data corresponding to the display element. For every display element in the panel, this process can be repeated to respectively control the light transmittance of each display element in the panel, and eventually a whole image can be presented. In other words, the liquid crystal display device 10 displays the image by controlling voltages of the proprietary electrode of the display element according to the data value in the incoming image. Meanwhile, the grey levels of different types of liquid crystal display device may not the same. Normally, the grey levels of the liquid crystal display device could vary from 4 bits to 8 bits. In general, from an ordinary customers' point of view, it has been widely recognized that the less the grey levels, the worse the image quality.
On the other hand, the number of bits of the incoming display data can be different. When the number of bits of the display data is greater than the number of bits which can be displayed by the display elements, according to the prior art, some display devices just simply discard the least significant bits of the display data, such that the truncated data can fit the data width of the display device and then can be displayed by the display devices. However, by doing so, the image quality can be sacrificed.
Furthermore, the display element should be able to constantly switch the polarity of its proprietary electrode relative to a common electrode, and this is very important and essential for the liquid crystal material in a display element to keep functioning normally. The method of switching the polarity of the display element is to switch the voltage of the proprietary electrode alternatively between a positive voltage and a negative voltage (relative to the common electrode), such that the liquid crystal material will not experience an irreversible change, and permanently destroys its function as an optical switch. Please refer to FIG. 2A and FIG. 2B, which illustrates a schematic diagram of a dot inversion liquid crystal display device 20 and the polarity distribution of display elements thereof. Inside FIG. 2A and FIG. 2B, the plus sign (+) means the polarity of the display element is of positive polarity, and the negative sign (−) is of the negative polarity. All the display elements should be able to switch between these two polarities. Normally, the display element should be able to switch the polarity of the display element for every new frame of data. For example, the polarity distribution of the dot inversion liquid crystal display device 20 is taking a single display element as a group, and any display element (group) DE_x,y must have its polarity opposite to the four neighboring display elements (groups). Noteworthily, the polarity distribution of the display elements of a panel will heavily depend on the original design of the liquid crystal display device. For example, please refer to FIG. 3A, which illustrates a schematic diagram of a two-dot inversion liquid crystal display device 30 and display elements thereof. The most distinguished feature of the two-dot inversion liquid crystal display device 30 is that any trace from the source driver (exampled and denoted as S1˜S3 in FIG. 3A) can supply up to two columns of display elements with the display data; the odd-numbered and the even-numbered traces from the gate driver (exampled and denoted as G1˜G7 in FIG. 3A) are designed to activate alternatively, so the display data can be written into the display elements in a seamless way. Please refer to FIG. 3B and FIG. 3C, which illustrate schematic diagrams of a two-dot inversion liquid crystal display device 30 and the polarity distribution of display elements thereof. The two-dot inversion liquid crystal display device 30 often utilizes the dual gate structure, such that two neighboring display elements of the same polarity can be taken as a group DEG_x,y. The display elements belonging to the same group DEG_x,y keeps the same polarity, and the polarity of the group is opposite to the polarities of its four neighboring groups. Besides, on the boundary portion of the two-dot inversion liquid crystal display device 30, it may have a polarity distribution where only one display element becomes a group. Please refer to FIG. 3D and FIG. 3E, which illustrate schematic diagrams of the two-dot inversion liquid crystal display device 30 with irregular polarity distribution on the boundary of the LCD panel.